x-pack/filebeat/input/httpjson: reorganise code to improve code local…

…ity (#36439)

* chain.go => config_chain.go
* simplify encoding registry
* simplify transform registry
    This removes the registration code and makes the use of the registry
    effectively local rather than a mutated global. It also simplifies the
    structure of the registry type.
* improve code locality of chain helpers
* improve code locality of request
    Use conventional ordering: type, constructor, methods and caller before
    callee in source order.
* improve code locality of response

x-pack/filebeat/input/httpjson/config_request.go

@@ -151,7 +151,7 @@ func (c *requestConfig) Validate() error {
 		return fmt.Errorf("unsupported method %q", c.Method)
 	}
 
-	if _, err := newBasicTransformsFromConfig(c.Transforms, requestNamespace, nil); err != nil {
+	if _, err := newBasicTransformsFromConfig(registeredTransforms, c.Transforms, requestNamespace, nil); err != nil {
 		return err
 	}
 

x-pack/filebeat/input/httpjson/config_response.go

@@ -37,10 +37,10 @@ type splitConfig struct {
 }
 
 func (c *responseConfig) Validate() error {
-	if _, err := newBasicTransformsFromConfig(c.Transforms, responseNamespace, nil); err != nil {
+	if _, err := newBasicTransformsFromConfig(registeredTransforms, c.Transforms, responseNamespace, nil); err != nil {
 		return err
 	}
-	if _, err := newBasicTransformsFromConfig(c.Pagination, paginationNamespace, nil); err != nil {
+	if _, err := newBasicTransformsFromConfig(registeredTransforms, c.Pagination, paginationNamespace, nil); err != nil {
 		return err
 	}
 	if c.DecodeAs != "" {
@@ -52,7 +52,7 @@ func (c *responseConfig) Validate() error {
 }
 
 func (c *splitConfig) Validate() error {
-	if _, err := newBasicTransformsFromConfig(c.Transforms, responseNamespace, nil); err != nil {
+	if _, err := newBasicTransformsFromConfig(registeredTransforms, c.Transforms, responseNamespace, nil); err != nil {
 		return err
 	}
 

x-pack/filebeat/input/httpjson/encoding.go

@@ -14,57 +14,8 @@ import (
 	"net/http"
 
 	"github.com/elastic/mito/lib/xml"
-
-	"github.com/elastic/elastic-agent-libs/logp"
-)
-
-type encoderFunc func(trReq transformable) ([]byte, error)
-
-type decoderFunc func(p []byte, dst *response) error
-
-var (
-	registeredEncoders             = map[string]encoderFunc{}
-	registeredDecoders             = map[string]decoderFunc{}
-	defaultEncoder     encoderFunc = encodeAsJSON
-	defaultDecoder     decoderFunc = decodeAsJSON
 )
 
-func registerEncoder(contentType string, enc encoderFunc) error {
-	if contentType == "" {
-		return errors.New("content-type can't be empty")
-	}
-
-	if enc == nil {
-		return errors.New("encoder can't be nil")
-	}
-
-	if _, found := registeredEncoders[contentType]; found {
-		return errors.New("already registered")
-	}
-
-	registeredEncoders[contentType] = enc
-
-	return nil
-}
-
-func registerDecoder(contentType string, dec decoderFunc) error {
-	if contentType == "" {
-		return errors.New("content-type can't be empty")
-	}
-
-	if dec == nil {
-		return errors.New("decoder can't be nil")
-	}
-
-	if _, found := registeredDecoders[contentType]; found {
-		return errors.New("already registered")
-	}
-
-	registeredDecoders[contentType] = dec
-
-	return nil
-}
-
 func encode(contentType string, trReq transformable) ([]byte, error) {
 	enc, found := registeredEncoders[contentType]
 	if !found {
@@ -81,35 +32,34 @@ func decode(contentType string, p []byte, dst *response) error {
 	return dec(p, dst)
 }
 
-func registerEncoders() {
-	log := logp.L().Named(logName)
-	log.Debugf("registering encoder 'application/json': returned error: %#v",
-		registerEncoder("application/json", encodeAsJSON))
-
-	log.Debugf("registering encoder 'application/x-www-form-urlencoded': returned error: %#v",
-		registerEncoder("application/x-www-form-urlencoded", encodeAsForm))
-}
-
-func registerDecoders() {
-	log := logp.L().Named(logName)
-	log.Debugf("registering decoder 'application/json': returned error: %#v",
-		registerDecoder("application/json", decodeAsJSON))
-
-	log.Debugf("registering decoder 'application/x-ndjson': returned error: %#v",
-		registerDecoder("application/x-ndjson", decodeAsNdjson))
-
-	log.Debugf("registering decoder 'text/csv': returned error: %#v",
-		registerDecoder("text/csv", decodeAsCSV))
-
-	log.Debugf("registering decoder 'application/zip': returned error: %#v",
-		registerDecoder("application/zip", decodeAsZip))
+var (
+	// registeredEncoders is the set of available encoders.
+	registeredEncoders = map[string]encoderFunc{
+		"application/json":                  encodeAsJSON,
+		"application/x-www-form-urlencoded": encodeAsForm,
+	}
+	// defaultEncoder is the decoder used when no registers
+	// encoder is available.
+	defaultEncoder = encodeAsJSON
+
+	// registeredDecoders is the set of available decoders.
+	registeredDecoders = map[string]decoderFunc{
+		"application/json":        decodeAsJSON,
+		"application/x-ndjson":    decodeAsNdjson,
+		"text/csv":                decodeAsCSV,
+		"application/zip":         decodeAsZip,
+		"application/xml":         decodeAsXML,
+		"text/xml; charset=utf-8": decodeAsXML,
+	}
+	// defaultDecoder is the decoder used when no registers
+	// decoder is available.
+	defaultDecoder = decodeAsJSON
+)
 
-	log.Debugf("registering decoder 'application/xml': returned error: %#v",
-		registerDecoder("application/xml", decodeAsXML))
-	log.Debugf("registering decoder 'text/xml': returned error: %#v",
-		registerDecoder("text/xml; charset=utf-8", decodeAsXML))
-}
+type encoderFunc func(trReq transformable) ([]byte, error)
+type decoderFunc func(p []byte, dst *response) error
 
+// encodeAsJSON encodes trReq as a JSON message.
 func encodeAsJSON(trReq transformable) ([]byte, error) {
 	if len(trReq.body()) == 0 {
 		return nil, nil
@@ -120,10 +70,12 @@ func encodeAsJSON(trReq transformable) ([]byte, error) {
 	return json.Marshal(trReq.body())
 }
 
+// decodeAsJSON decodes the JSON message in p into dst.
 func decodeAsJSON(p []byte, dst *response) error {
 	return json.Unmarshal(p, &dst.body)
 }
 
+// encodeAsForm encodes trReq as a URL encoded form.
 func encodeAsForm(trReq transformable) ([]byte, error) {
 	url := trReq.url()
 	body := []byte(url.RawQuery)
@@ -135,6 +87,8 @@ func encodeAsForm(trReq transformable) ([]byte, error) {
 	return body, nil
 }
 
+// decodeAsNdjson decodes the message in p as a JSON object stream
+// It is more relaxed than NDJSON.
 func decodeAsNdjson(p []byte, dst *response) error {
 	var results []interface{}
 	dec := json.NewDecoder(bytes.NewReader(p))
@@ -149,6 +103,7 @@ func decodeAsNdjson(p []byte, dst *response) error {
 	return nil
 }
 
+// decodeAsCSV decodes p as a headed CSV document into dst.
 func decodeAsCSV(p []byte, dst *response) error {
 	var results []interface{}
 
@@ -189,6 +144,7 @@ func decodeAsCSV(p []byte, dst *response) error {
 	return nil
 }
 
+// decodeAsZip decodes p as a ZIP archive into dst.
 func decodeAsZip(p []byte, dst *response) error {
 	var results []interface{}
 	r, err := zip.NewReader(bytes.NewReader(p), int64(len(p)))
@@ -225,6 +181,7 @@ func decodeAsZip(p []byte, dst *response) error {
 	return nil
 }
 
+// decodeAsXML decodes p as an XML document into dst.
 func decodeAsXML(p []byte, dst *response) error {
 	cdata, body, err := xml.Unmarshal(bytes.NewReader(p), dst.xmlDetails)
 	if err != nil {

x-pack/filebeat/input/httpjson/input.go

@@ -265,6 +265,43 @@ func newNetHTTPClient(ctx context.Context, cfg *requestConfig, log *logp.Logger,
 	return netHTTPClient, nil
 }
 
+func newChainHTTPClient(ctx context.Context, authCfg *authConfig, requestCfg *requestConfig, log *logp.Logger, reg *monitoring.Registry, p ...*Policy) (*httpClient, error) {
+	// Make retryable HTTP client
+	netHTTPClient, err := newNetHTTPClient(ctx, requestCfg, log, reg)
+	if err != nil {
+		return nil, err
+	}
+
+	var retryPolicyFunc retryablehttp.CheckRetry
+	if len(p) != 0 {
+		retryPolicyFunc = p[0].CustomRetryPolicy
+	} else {
+		retryPolicyFunc = retryablehttp.DefaultRetryPolicy
+	}
+
+	client := &retryablehttp.Client{
+		HTTPClient:   netHTTPClient,
+		Logger:       newRetryLogger(log),
+		RetryWaitMin: requestCfg.Retry.getWaitMin(),
+		RetryWaitMax: requestCfg.Retry.getWaitMax(),
+		RetryMax:     requestCfg.Retry.getMaxAttempts(),
+		CheckRetry:   retryPolicyFunc,
+		Backoff:      retryablehttp.DefaultBackoff,
+	}
+
+	limiter := newRateLimiterFromConfig(requestCfg.RateLimit, log)
+
+	if authCfg != nil && authCfg.OAuth2.isEnabled() {
+		authClient, err := authCfg.OAuth2.client(ctx, client.StandardClient())
+		if err != nil {
+			return nil, err
+		}
+		return &httpClient{client: authClient, limiter: limiter}, nil
+	}
+
+	return &httpClient{client: client.StandardClient(), limiter: limiter}, nil
+}
+
 // clientOption returns constructed client configuration options, including
 // setting up http+unix and http+npipe transports if requested.
 func clientOptions(u *url.URL, keepalive httpcommon.WithKeepaliveSettings) []httpcommon.TransportOption {

x-pack/filebeat/input/httpjson/input_manager.go

@@ -41,11 +41,6 @@ func NewInputManager(log *logp.Logger, store inputcursor.StateStore) InputManage
 
 // Init initializes both wrapped input managers.
 func (m InputManager) Init(grp unison.Group, mode v2.Mode) error {
-	registerRequestTransforms()
-	registerResponseTransforms()
-	registerPaginationTransforms()
-	registerEncoders()
-	registerDecoders()
 	return multierr.Append(
 		m.stateless.Init(grp, mode),
 		m.cursor.Init(grp, mode),